Paving machines are commonly employed in the laying of bituminous roadway mat. The typical paving machine employs a "floating screed" for spreading and compressing the bituminous material to form a smooth surfaced roadway mat. While in the past it has been common to use a floating screed of fixed width, for example, on the order of eight feet or ten feet in width, it has been discovered that the efficiency of the paving machine can be increased and the number of trips required to generate a road surface can be decreased by employing a floating screed having an operator selectable width. This may be accomplished by providing a series of extensions which may be affixed to the main body of the floating screed to a predetermined fixed width. However, a more advantageous arrangement of the floating screed includes one, or more typically two, screed extensions which are slidingly attached to the main body of the floating screed. These screed extensions are typically connected to a linear power source such as a bi-directional hydraulic cylinder or other similar activator, which is selectively operable in response to controls disposed at the operator's control station. This permits the operator to control the position of the screed extensions in response to changing requirements as the paving machine progresses. For example, this permits the screed operator to accommodate obstacles in the path of the paving machine such as sewer drains and manhole covers, and also to permit overwidth paving of the road surface to accommodate driveway entrances and other similar areas where overwidth paving of the roadway mat is desired.
The floating screed type paving machine is typically a self-propelled tractor unit providing a storage means for receiving and containing a discreet quantity of loose bituminous aggregate and a material flow means for conveying the bituminous aggregate to the roadbed where the loose bituminous aggregate is then displaced laterally in front of the floating screed. As the paving machine progresses along the roadbed, the floating screed engages the loose bituminous aggregate, plowing under and compressing the bituminous aggregate into the desired roadway mat. It is common to provide endgates on the outer, distal ends of the screed extensions to ensure that the loose bituminous aggregate disposed in front of the screed extensions is not merely shunted aside beyond the width of the floating screed. The means most commonly used for providing the lateral disposition of the loose bituminous aggregate is a flighted auger providing two oppositely directed flights from the centerline of the paving machine to provide disposition of an equal amount of bituminous aggregate toward the outer edges of the floating screed. While this means has proved to be generally satisfactory, a difficulty exists in ensuring that the appropriate desired amount of loose bituminous aggregate is provided to the screed extensions. This problem is exacerbated by the fact that paving machines are often operated under less than ideal conditions, and it is often necessary to operate one screed extension at a different width than the other screed extension as obstacles are passed or width changes in the roadway mat must be accommodated as the paving machine moves forward. It is necessary for the screed operator to ensure that a suitable proportion of loose bituminous aggregate is available to ensure satisfactory completion of the roadway mat in connection with the furthest extended screed extension, and this causes an undesirable accumulation of bituminous aggregate in front of the less far extended screed extension, due to the fact that there is a reduced amount of area to be covered under that floating screed extension. Furthermore, even where the screed extensions are extended to similar widths, it is undesirably difficult for the screed operator to assure that the desired amount of loose bituminous aggregate is provided for the floating screed. In the operation of current paving machines, the screed operator must cause a suitable flow of loose bituminous aggregate to the auger to ensure that a sufficient amount of aggregate will cascade across the floating screed to reach and fill the area in front of the floating screed to the minimum requisite depth required for the pavement mat. However, the screed operator must be possessed of a substantial amount of skill and expertise to accomplish this result due to the fact that the primary means of controlling the amount of aggregate available to the floating screed is in the conveyance means from the tractor unit of the paving machine.
Therefore, it is an object of the present invention to provide an improved material flow management system for a paving machine.
It is another object of the present invention to provide such a material flow management system as will provide improved control of the aggregate available to the floating screed.
It is a further object of the present invention to provide such a material flow management system as will provide improved control of the material flow to the screed extension.
It is yet another object of the present invention to provide such a material flow management system as will be selectively controllable by the screed operator.
It is yet a further object of the present invention to provide such a material flow management system as will relatively inexpensive to manufacture.
It is another object of the present invention to provide such a material flow management system as will be readily applied to paving machines and such as will not require substantial modification of a paving machine.
It is yet a further object of the present invention to provide such a material flow management system as will be inexpensive to maintain and will be durable.
It is yet a further object of the present invention to provide such a material flow management system as will provide an intermediate boundary to aid a screed operator in controlling the disposition of loose bituminous aggregate in front of the floating screed of a paving machine.